The present invention relates to an apparatus for determining crosswind effects on vehicles, in particular motor vehicles, having a measuring and computing device which evaluates pressure differences occurring in the case of a crosswind between measuring points on opposite sides of the vehicle, in particular in the region of the front corners of the vehicle. A signal representing the direction of the wind relative to the vehicle is formed by the quotient of a first pressure difference between a first measuring point on one side of the vehicle and a second measuring point, asymmetric thereto, on the other side of the vehicle and of a second pressure difference between a third measuring point on one side of the vehicle and a fourth measuring point, asymmetric thereto, on the other side of the vehicle. A signal representing the dynamic pressure of the crosswind is determined from the multiplication of the pressure difference between two measuring points situated asymmetrically to one another on opposite sides of the vehicle with a predeterminable factor which is dependent on the signal representing the direction of the wind.
Such an apparatus is described in German Patent No. 38 16 057. In the determination of the direction of the wind in this known patent, use is made of the fact that, in the case of a crosswind, flow around a vehicle formed symmetrically to the vertical longitudinal center plane in the customary fashion is asymmetric to the vertical longitudinal center plane. According to this earlier patent application, the degree of asymmetry and hence the angle of incidence of the crosswind relative to the vehicle can be determined by evaluating the pressure at a small number of measuring points at the outside of the vehicle. To determine the dynamic pressure, it is then sufficient to determine a pressure difference at two measuring points positioned on both sides of the vehicle, it being necessary in addition for this pressure difference to be multiplied by a correction factor correlated with the angle of incidence.
According to the earlier patent application, differential pressure gauges are preferably arranged at the outside, at the respective measuring points. These pressure gauges measure the pressure difference between their outward-facing side and their inside, which is connected via tube or hose lines to a reference chamber common to all the differential pressure gauges. The reference chamber is designed and arranged in such a way that any pressure fluctuations which occur in this chamber take place considerably more slowly than pressure changes occurring at the outside of the differential pressure gauges and hence outside the vehicle, in particular those which are caused by crosswind.
Account is taken of the fact that differential pressure gauges operate relatively precisely (even inexpensive gauges), and knowledge of the absolute pressure values at the respective measuring points is not necessary for the determination of the angle of incidence or the dynamic pressure of the crosswind.
According to German Patent 38 16 057, the measuring points or the differential pressure gauges are arranged in particular in the region of the front corners of the vehicle because particularly large crosswind-dependent pressure differences occur there.
Provision is furthermore made according to this known patent for the differential pressure gauges to be fitted near the outward-leading mouths of the tube or hose lines connected to the common reference chamber in order to guarantee that the differential pressure gauges can react virtually without delay to pressure changes of the air at the outside of the vehicle.
An object of the present invention is to further simplify an apparatus for determining the crosswind effect on motor vehicles.
This and other objects are achieved according to embodiments of the present invention by the fact that to determine the pressure differences at least two differential pressure sensors are connected between in each case two conduits (e.g. tubes or hoses) of the same type which, with their open ends remote from the respective differential pressure sensor, open to the outside at mutually asymmetric points on both sides of the longitudinal axis of the vehicle, and that the open ends of the conduits are arranged at openings of a bumper which also accommodates the conduits and the associated differential pressure sensors.
In the present invention, use is made of the surprising fact that the pressure differences at the mouths of the conduits associated with a differential pressure sensor can be determined virtually instantaneously by means of the differential pressure sensor because pressure changes at the mouths propagate towards the differential pressure sensor at extraordinarily high speed in the conduits. Even at an inside diameter of the conduits of 1 mm, it is possible (at least if, as in normal vehicles, the length of the conduits is of the order of about 1 m) to count on a propagation speed of the pressure changes in the conduits in the range of the speed of sound in air. The invention thus makes it possible to determine the pressure difference at two measuring points at a distance from one another with in each case only one differential pressure sensor, with the result that the number of pressure sensors remains small even for a relatively large number of measuring points. Accordingly, the performance requirements of the computer used for evaluation of the sensor signals also remain relatively low.
By arranging the conduits and the associated sensors at the bumpers of the vehicle, it is possible to retrofit a motor vehicle with an apparatus for determining crosswind effects without the need to carry out significant work on the vehicle body. Moreover, the bumpers of all motor vehicles offer sufficient space to accommodate the apparatus according to the invention, and this with a minimum expenditure in terms of construction.
It can furthermore be expedient to accommodate the differential pressure sensors together with a thermocouple in a box or housing or in a hollow at the bumper, such that all differential pressure sensors are exposed to approximately the same temperature. In this way, there is the possibility of taking into account the respective temperature with the thermocouple and compensating any temperature drift of the differential pressure sensors.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.